如果DNS超时导致永久电子邮件失败？

有时，发送给使用outlook.com系统作为其电子邮件服务器的收件人时，电子邮件将无法通过。 他们的MXlogging可以解决，但他们的Alogging（如example-com.mail.protection.outlook.com ）超时。

在这里使用sendmail ，我不是专家。 我inheritance了这个configuration，并且不太了解这些设置。 我所知道的一件事情是，它已经多年没有被编辑过了，没有任何迹象表明存在问题。

我不知道是不是有意为之，但是从dig example-com.mail.protection.outlook.com的响应时间过了15秒后，再后来挖的都成功了。

我们正在使用我们自己的BIND DNS服务器进行caching，至less这么长时间还没有重新configuration。

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看起来我们的sendmail系统在得到主机后没有findexample-com.mail.protection.outlook.com 。 这种永久失败是否合适？ 应该改为临时失败吗？ 标准是什么？ 是outlook.com错误或我们的sendmail？

编辑

以下是maillog的相关日志条目，其中敏感信息masked example.com代表收件人服务器， example.net代表我们自己的domain 。

 Jun 16 09:28:28 myhostname sendmail[8613]: [ID 801593 mail.info] s5GDSOZ4008613: from=websusr, size=16975, class=0, nrcpts=2, msgid=<[email protected]>, relay=websusr@localhost Jun 16 09:28:28 myhostname sendmail[8617]: [ID 801593 mail.info] s5GDSSIP008617: from=<[email protected]>, size=17222, class=0, nrcpts=2, msgid=<[email protected]>, proto=ESMTP, daemon=MTA-v4, relay=localhost [127.0.0.1] Jun 16 09:28:28 myhostname sendmail[8613]: [ID 801593 mail.info] s5GDSOZ4008613: to="John Doe" <[email protected]>, ctladdr=websusr (60001/60001), delay=00:00:04, xdelay=00:00:00, mailer=relay, pri=76975, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s5GDSSIP008617 Message accepted for delivery) Jun 16 09:32:09 myhostname sendmail[8618]: [ID 801593 mail.info] s5GDSSIP008617: to=<[email protected]>, ctladdr=<[email protected]> (60001/60001), delay=00:03:41, xdelay=00:03:40, mailer=esmtp, pri=77440, relay=example-com.mail.eo.outlook.com., dsn=5.1.2, stat=Host unknown (Name server: example-com.mail.eo.outlook.com.: host not found) Jun 16 09:32:09 myhostname sendmail[8618]: [ID 801593 mail.info] s5GDSSIP008617: s5GDW9IP008618: DSN: Host unknown (Name server: example-com.mail.eo.outlook.com.: host not found) 

也就是刚才的dig输出，虽然目前这个问题没有发生，但是它可以让你看到mxlogging。

 >dig example.com mx ; <<>> DiG 9.3.2 <<>> example.com mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1448 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 4, ADDITIONAL: 0 ;; QUESTION SECTION: ;example.com. IN MX ;; ANSWER SECTION: example.com. 3461 IN MX 0 example-com.mail.protection.outlook.com. example.com. 3461 IN MX 10 example-com.mail.eo.outlook.com. ;; AUTHORITY SECTION: example.com. 86261 IN NS ns1.example.org. example.com. 86261 IN NS ns2.example.org. ;; Query time: 0 msec ;; SERVER: 10.0.0.109#53(10.0.0.109) ;; WHEN: Thu Jul 3 09:32:08 2014 ;; MSG SIZE rcvd: 215 >dig example-com.mail.protection.outlook.com ; <<>> DiG 9.3.2 <<>> example-com.mail.protection.outlook.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1734 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 6 ;; QUESTION SECTION: ;example-com.mail.protection.outlook.com. IN A ;; ANSWER SECTION: example-com.mail.protection.outlook.com. 10 IN A 207.46.163.170 example-com.mail.protection.outlook.com. 10 IN A 207.46.163.215 example-com.mail.protection.outlook.com. 10 IN A 207.46.163.138 ;; AUTHORITY SECTION: mail.protection.outlook.com. 1800 IN NS ns1-proddns.glbdns.o365filtering.com. mail.protection.outlook.com. 1800 IN NS ns2-proddns.glbdns.o365filtering.com. ;; ADDITIONAL SECTION: ns1-proddns.glbdns.o365filtering.com. 30 IN A 207.46.100.42 ns1-proddns.glbdns.o365filtering.com. 30 IN A 207.46.163.143 ns1-proddns.glbdns.o365filtering.com. 30 IN A 207.46.163.176 ns2-proddns.glbdns.o365filtering.com. 30 IN A 207.46.163.176 ns2-proddns.glbdns.o365filtering.com. 30 IN A 207.46.100.42 ns2-proddns.glbdns.o365filtering.com. 30 IN A 207.46.163.143 ;; Query time: 464 msec ;; SERVER: 10.0.0.109#53(10.0.0.109) ;; WHEN: Thu Jul 3 09:33:30 2014 ;; MSG SIZE rcvd: 276 >dig example-com.mail.eo.outlook.com ; <<>> DiG 9.3.2 <<>> example-com.mail.eo.outlook.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 940 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 12 ;; QUESTION SECTION: ;example-com.mail.eo.outlook.com. IN A ;; ANSWER SECTION: example-com.mail.eo.outlook.com. 10 IN A 207.46.163.138 example-com.mail.eo.outlook.com. 10 IN A 207.46.163.170 example-com.mail.eo.outlook.com. 10 IN A 207.46.163.247 ;; AUTHORITY SECTION: mail.eo.outlook.com. 5450 IN NS ns1-prodeodns.glbdns.o365filtering.com. mail.eo.outlook.com. 5450 IN NS ns2-prodeodns.glbdns.o365filtering.com. ;; ADDITIONAL SECTION: ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 157.55.234.42 ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 157.56.112.42 ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.100.42 ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.163.143 ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.163.176 ns1-prodeodns.glbdns.o365filtering.com. 30 IN A 65.55.169.42 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 65.55.169.42 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 157.55.234.42 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 157.56.112.42 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.100.42 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.163.143 ns2-prodeodns.glbdns.o365filtering.com. 30 IN A 207.46.163.176 ;; Query time: 248 msec ;; SERVER: 10.0.0.109#53(10.0.0.109) ;; WHEN: Thu Jul 3 09:33:45 2014 ;; MSG SIZE rcvd: 368 >